# Technical Support Document for U.S. EPA’s Proposed Rule for Addition of

a Subsurface Intrusion Compone nt to the Hazard Ranking System 

# Appendix D: Site Summaries and Scoring Information for Test Sites (Tier 1)

Test Site 001: District of Columbia

Test Site 002: Maryland

Test Site 003: District of Columbia

Test Site 004: Maryland

Test Site 005: Pennsylvania

Test Site 006: Texas

Test Site 007: District of Columbia

Test Site 008: Montana

Test Site 009 : Wisconsin

Test Site 010 : M issouri

Test Site 011 : M innesota

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# Scoring Information for Test Sites (Tier 1)

As part of the evaluation of the need for the proposed subsurface intrusion ( SsI ) addition to the Hazard Ranking System ( HRS ), efforts to identify and classify sites with suspected impacts from SsI were undertaken. The sites identified and classified as a part of this effort are identified and classified in further detail in appendix A. Eleven of the identified sites were determin ed to have a subsurface threat and sampling data sufficient to indicate that these sites would not result in a significant HRS site score with the inclusion of the proposed SsI addition. These sites were classified as Tier 1 sites in the SsI Inventory of S ites. Using available sampling data, these 11 sites were used to test and evaluate the proposed HRS SsI addition.
The following evaluations of the 11 test site s contain summaries of the sites with brief introductions on the sites, outline s of the scoring a pproach for each site and annotated scoresheet s indicating the rationale for the calculated HRS site score using the SsI component and other current HRS pathways, as applicable, with available data. Due to limited information available, t hese site summarie s include the key

- site specific scoring limitations and assumptions used in the evaluation of these sites with the proposed SsI addition. The summaries provided below are intended for testing purposes are not intended to justify the pla cement of these sit es on the National Priorities List

.

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### Page D -3 

# Subsurface Intrusion Test Site 001 ( January 2016 )

Site Description Test site 001 consists of a chlorinated solvents release from a n operating drycleaner situated adjacent to a daycare and a private school. The U.S. Environmental Protection Agency ( EPA ) determined that exhaust from the drycleaner was causing elevated levels of tetrachloroethylene (PCE) and trichloroethylene (TCE) to b e taken into nearby building ventilation systems. EPA has collected indoor air samples from the dr ycleaner, daycare
, and private school and has also collected soil gas samples from beneath the foundations (i.e., subslab) of surrounding residential and commercial buildings, including the drycleaner, daycare and private school . Additionally, EPA has also collected outdoor air samples

. The site includes an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. Tetrachloroethene was documented to be present in the AOE in the daycare facility and private school.

The site additionally includes an area of subsurface contamination (ASC) delineated by subslab samples meeting observed release criteria. The structures within the ASC include two commercial buildings, one residential home and a church

. Scoring Limitations/Assumptions Besides the assumptions made for all test sites listed at the beginning of this appendix, the following site

specific limitations and assumptions were identified for scoring this site:

• It is assumed that all regularly occupied structures within the AOE and the ASC have a non

- zero structure containment value.

• The online databases (i.e., http://www.privateschoolreview.com and http://www.childcarecenter.us/ ) used to estimate the number of students and workers at the nearby contaminated daycare and school represent s current conditions. The buildings comp ri sing the contaminated daycare and school are structurally interconnected

. • Indoor air samples meeting the observed exposure criteria are not due to anthropogenic sources (e.g., potential indoor sources of vapor

- forming chemicals, such as household cleaners ) and the significant increase in hazardous substance concentrations are attributable at least in part to the release(s) being evaluated.

• Outdoor contaminated air (measured during one of the three sampling events when the dry cleaner was in operation) is not the source of the indoor air contamination

. • Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 ful l- time worker per workplace if more specific information is not available.

### Page D -4 

### • An indoor air temperature of 25 °C and 1 standard atmosphere were assumed when converting indoor air sampling data provided in units of parts per billion by volume (ppbv ) for comparison to health

based benchmarks (i.e., from ppbv to micrograms per cubic meter [μg/m 3 

### ]).

• Per the draft HRS addition, An assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structures).

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• The HRS scoring d oes not include people residing in what appears to be apartments located above or behind the school, daycare and drycleaner facilities, as there was not sufficient information available to evaluate them.

• The depth below ground surface at which the subslab sample was collected at the regularly occupied residential struct ure identified within the ASC is unknown. It is assumed for evaluation purposes that the sample was collected within five feet of the structure.

The figure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS . The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be neces sary to determine if the site would qualify for listing.

As part of this limited assessment, t est site 001 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

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# Subsurface Intrusion Test Site 00 1 ( Figure 1 )

Site Diagram

### Page D -6 

## Table 5

- 11 Subsurface Intrusion Component Scoresheet Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Likelihood of Exposure:
1. Observed Exposure
An o bserved exposure by chemical analysis for PCE w as documented in two regularly occupied structures

. 550 550

2. Potential for Exposure

Per the draft HRS, the p otential for exposure factor was not evaluated based on the documentation of an observed exposure. 2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15

- 2d. Vapor Migration Potential 25

- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3 ) 550 550
Waste Characteristics:

5. Toxicity/ D egradation The highest toxicity value for the substances documented in an ASC o r the area of observed exposure (AOE) is 1,000 for TCE

. Per the draft HRS, although TCE was not found in a sample that met observed exposure criteria, as the depth to contamination = is less than 10 feet, a degradation factor of one is assigned . The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 1,000 , which is the highest combined value of all eligible substances. (a) 1,000

6. Hazardous Waste Quantity
The actual basal area footprint s of the six regularly occupied structures in the AOE and ASC are unknown

. Therefore, as stated in the draft HRS, a value of 1,740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity , which was used to select a hazardous waste quantity factor value using HRS Table s 5

- 18 (draft) and 2

- 6. (a) 100

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 5 was used to select a waste characteristics factor category value of 18 from the draft HRS Table 2

- 7. 100 18

Targets:
8. Exposed Individual
T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations . Per the draft HRS, a value of 50 is assigned. 50 50

9. Population:
9a . Level I Concentrations
The estimated population attending the daycare and school is 169 and approximately 10 full

- time staff at the daycare facility and 1 9 full

- time staff at the (b) 1786

### Page D -7 school located within the with in the AOE , which contain PCE concentrations greater than the applicable health

- based benchmark of 9. 3 μg/m 3 (Cancer Risk Screening Concentration)
, is 169 . Per the draft HRS, the total number of workers are divided by 3(29/3=9.6) and summed with the population attending the school and day care, which is 9.6 + 169 = 178.6. T his value is then multiplied by a weighting factor of 10.
9b . Level II Concentrations
No regularly occupied structures subject within the AOE

. to Level II concentrations are present (b) 0

9c. Population within Area(s) of Subsurface Contamination
The actual population present within the three regularly occupied structures (one commercial facility, one religious facility and one residence) located with in the ASC is unknown

. Per the draft HRS
, for a residence, an average of 2. 17 persons per household associated with the area in which the site is located results in a n estimate of 2. 17 people ; Worker population is assumed to be at least 1 full

- time worker per facility, resulting in a worker population of 2 workers divided by 3 (.7) in the ASC. The populations are summed (2.87). A subslab sample meeting observed release criteria was taken at the residence ; the refore, this population estimate was multiplied by a weighting factor of 0.4 using the draft HRS Table 5

- 20. This results in a population estimate of 1.15 for the ASC

. (b) 1.15

9 d

. Total Population (lines 9a + 9b + 9c) (b) 1,787.15
10. Resources
There is one religious facility (a place of potential are unknown ) within the ASC

. Per the draft HRS, worship , but building activities a value of 5 is assigned. 5 5

11. Targets (lines 8 + 9 d + 10) (b) 1,842. 1

Subsurface Intrusion Component Score

12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 1 1 )/82,500 c (subject to a 100 100 .00

Soil Exposure and Subsurface Intrusion Pathway Score
13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 100 .00

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer

.

HRS Site Score Maximum Value Value Assigned √[ ( S gw 2 + S sw 2 + S sessi 2 + S a 2 )/4] = √ [( 0 2 + 0 2 + 100 2 +0 2 )/4] 100 50

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# Subsurface Intrusion Test Site 00 2 ( January 2016 )

Site Description Test site 002 is located in central Maryland
, within an area of commercial and residential land use types. The subject property consists of an L- shaped shopping center strip and three pad sites consisting of multisubunit structures . Historical operations have resulted in a release of chlorinated solvents to shallow ground water and soils immediately surrounding t he facility. Dry cleaning facilities are documented to have been ongoing for approximately 40 years – the current tenant ceased on -site dry cleaning operations in 2004. This site has been investigated on multiple occasions that have included indoor air sampling in January, July and November of 2013. Additionally, ground water samples have been collected on multiple occasions dating back to November 2007.

The site includes an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. T he hazardous substances documented to be present in the AOE were tetrachloroethene (PCE) , trichloroethene (TCE) , and cis -1, 2-dichloroethene. The structures within the AOE include 17 multi -subunit structures and 29 residential homes.

The site additionally includes an area of subsurface contamination (ASC) delineated by ground water samples meeting observed release criteria. Additional structures within the ASC include 8 multi-subunit
structures

.
Scori ng Limitations and AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptions were identified for scoring this site:

• For the soil gas and indoor air sampling events
, no appropriate backgro und sample was available ; it was assumed that the background level to compare against release contaminant concentrations was non-detect for manufactured substances (e.g., PCE/TCE ). Therefore, per the draft HRS Subsurface Intrusion ( SsI ) Addition (draft HRS addition), an observed exposure or observed release was documented when a release contaminant concentration equaled or exceeded its appropriate reporting limit.

• It is assumed that all regularly occupied structures within the AOE and ASC have a non

- zero structure containment value.

• Indoor air samples meeting the observed exposure criteria are not due to the presence of potential indoor sources of vapor- forming chemicals, such as household cleaners, and the significant increase in hazardou s substance levels are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual ex tent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

time worker per workplace if more specific information is not available.

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- 9 

### • Per the draft HRS addition a n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structures).

.

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• It is assumed that all ground water sampling data used in this analysis, including samples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• Hazardous Waste Quantity: Each apartment and townhouse building is assumed to be comprised of either 4 or 5 separate building sub units. This evaluation inc ludes 14 building sub units in three buildings . Each sub unit is assumed to contain 4 separate apartments. The high

- rise apartment is assumed as one building un it with 13 apartments per floor (468 units, 12 floors per building, three buildings).

• As part of this evaluation, it is assumed that the high

- rise apartment floors are interconnected within a building and therefore all 13 apartments per floor are considered. The apartment and townhouse building is assumed to be interconnected at the sub unit level where each sub unit contains 2 ground level apartments.

The f i gure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the National Prioriti es List ( NPL ) , and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As p art of this limited assessment, the t est site 002 was evaluated using only the draft HRS su bsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS

.

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# Subsurface Intrusion Test Site 00 2 ( Figure 2 )

Site Diagram

### Page D -1 1 

### T able 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component
Likelihood of Exposure:

1. Observed Exposure An observed exposure by chemical analysis for tetrachloroethene, trichloroethene (TCE), and cis

- 1,2

- dichloroethene has been documented in eight regularly occupied structures. 550 550

2. Potential for Exposure
P er the draft HRS addition, the p otential for exposure factor was not evaluated based on the documentation of an observed exposure.

.

2a. Structure Containment 10 NS
2b. Depth to contamination 10 NS
2c. Vertical Migration 15 NS
2d. Vapor Migration Potential 25 NS

3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500 NS
4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Toxicity/ D egradation The highest toxicity value for any of the substances documented in the AOE or ASC is 10 ,000 for Vinyl Chloride

. Per the draft HRS addition, a lthough Vinyl Chloride was not found in a sample that met observed exposure criteria
, as the depth to contamination is less than 10 feet a degradation factor value of one is assigned

. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10 ,000

6. Hazardous Waste Quantity The actual basal area footprints of the 54 regularly occupied structures in the AOE and ASC are unknown . Per the draft HRS addition, for Tier D, Area, a value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity. These values were used to select a hazardous waste quantity factor value using HRS Tables 5

- 18 (draft addition) and 2

- 6. (a) 100

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 5 was used to select a waste characteristics factor category value of 18 from the draft HRS Table 2

- 7. 100 32

Targets:

### Page D -1 2 Factor Categories and Factors Maximum Value Value Assigned

8. Exposed Individual
T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations for PCE. Per the draft HRS addition, a value of 50 was assigned. 50 50

9. Population:

9a. Level I Concentrations
The a ctual population living in the three regularly occupied structures containing concentrations above the applicable health

- based benchmark of 9.3 μg/m 3 (Cancer Risk Screening Concentration) for PCE is unknown. Per the draft HRS addition, using the average of 2.79 persons per household for the county in which the site is located results in a total population estimate of 8.37 people exposed to Level I concentrations. This value is then multiplied by a weighting factor of 10 per the draft HRS addition. (b) 83.7

9b. Level II Concentrations
The a ctual population living in the 43 regularly occupied structures (26 residential homes ; one multi

- subunit apartment with 13 units ; 8 multi

- subunit apartments with 2 units each ; 8 multi

- subunits with at least one full

- time worker – total of 63 structures ) containing concentrations above the sample quantitation limit for PCE is unknown. Per the draft HRS addition, the total number of full

- time workers are divided by 3 (8/3=2.6) and summed with the population residing in the remaining structures. U sing the average of 2.79 persons per household for the county in which the site is located results in a total population estimate of 15 6.0 (153.4+2.6=156.0) people exposed to Level II concentrations in the remaining 35 structures

. (b) 156 .0

9c. Population within Area(s) of Subsurface Contamination
There are 8 regularly occupied structures ( 6 multi

- subunit apartments and 2 multi

- subunits with at least one full time worker ) within th e ASC that are delineated with soil gas samples as well as with ground water samples approximately eight to ten feet bgs.
Per the draft HRS addition, the total number of full

- time workers are divided by 3 (2/3=0.6) and summed with the population residing in the remaining structures. The actual population living in the remaining structure s is unknown. Per the draft HRS addition , using the average of 2.79 persons per household for the county in which the site is located results in a population estimate of 33.48 (

based on ground water samples ) (33.48+0.6 = 34.08)

. These population estimate s were multiplied by a weighting factor of 0.1 (ground water ) using the draft HRS addition Table 5

- 20.This results in a population estimate of 3. 4 for the ASC. (b) 3 .4

9d . Total Population (lines 9a + 9b + 9c) (b ) 243 .1

10. Resources No resources were identified within the AOE or ASC. Per the draft HRS addition, a value of 0 is assigned. 5 0

### Page D -1 3 Factor Categories and Factors Maximum Value Value Assigned

11. Targets (lines 8 + 9d + 10) (b) 293.1

Subsurface Intrusion Component Score

12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 c (subject to a 100 62. 52

Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 62. 52

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer



### .

HRS Site Score Maximum Value Value Assigned √[ 2 ( S gw + 2 S sw + 2 S s es si + S a 2 )/4] = √ [( 0 2 + 0 2 + 62. 52 2 +0 2 )/4] 100 31

. 26

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# Su bsurface Intrusion Test Site 003 ( January 2016 )

Site Description T est site 003 is located in the District of Columbia , within an area of residential homes and a church

. Previous investigations to assess a gasoline spill from a service station have identified ground water contaminated with tetrachloroethylene (PCE) and other chlorinated and non- chlorinated volatile organic analytes. Th e contamination appears to be traceable to a dr y cleaning operation. The PCE contamination was first detected in 2002 and subsequent investigations in 2003 and 2004 were conducted to determine the extent of the PCE contamination and to evaluate the extent of vapor intrusion into overlying residential s tructures.

The sit e includes an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. The hazardous substance documented to be present in the AOE was tetrachloroethylene (PCE) . The structures within the AOE include 57 multi -subunit regularly occupied structures.

The sit e additionally includes an area of subsurface contamination (ASC) delineated by ground water samples meeting observed release criteria. Additional structures within the ASC include two regula rly occupied structures and 63 multi

- subunit regularly occupied structures



## . Scoring Li mitations/AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptions were made in the scoring of this site:

• It i s a ssumed that all regularly occupied structur es w ithin th e AOE and ASC have a non-z ero structur e containment value.

• Indoor air samples meeting the observed exposure criteria are not due to the presence of potentia l indoor sources of vapor-f orming chemicals, such as h ousehold cleaners, and th e s ignifican t increas e in hazard ou s s ub stan ce level s ar e a ttributabl e at least in part to th e release(s) being evaluated.

• Dat a q uality i s sufficient for u se in testing th e d raft subsurf ace intrusion component.

• Sampling location s p resented ar e a pproximat e a nd may not represent th e actual extent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residentia l targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

tim e w o rker per workpla ce if mor e s pecifi c i nformation i s n ot available.

• Per the draft HRS addition, an assig ned ar ea v alu e o f 1,740 squar e feet i s u sed in determining a wast e quantity estimat e f or all regularly o ccupied structure s (including multi -subunit structures).

• Information used in th e s coring of th e test sit es (including aerial imagery) i s r epresen tative of
current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plum es r esulting from multipl e r eleases.

### Page D -1 5 

### • It is assumed that all ground water sampling data used in this analysis , including sam ples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• Aerial imagery, obtained through the maps.google.com online database was used to identify occupied structures for the purposes of th is analysis. These images are assumed to represent current conditions and that all residences are occupied. In several instances, structures were classified as duplex units based on these images and this information has not been validated. It is also assum ed that each structure and/or duplex unit identified is currently occupied.

• Although some reports indicate the presence of vapor mitigation systems, it is assumed that cracks and/or preferential pathways into a structure still exist and that all structures have a containment value greater than zero.

The figure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List (NPL) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As par t of this limited assessment, t est s ite 003 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

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# Subsurface Intrusion Test Site 00 3 ( Figure 3 )

Site Diagram

### Page D -1 7 

## Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Likelihood of Exposure:
1. Observed Exposure

An observed e xposure by chemical analysis for PCE was documented in six regularly occupied structures. 550 550

2. Potential for Exposure

Potential for exposure was not evaluated based on the documentation of an observed exposure per the HRS.
2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15

- 2d. Vapor Migration Potential 25

- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500 - 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550
Waste Characteristics:

5. Toxicity/ D egradation

The highest toxicity value for the substances documented in the area of subsurface contamination and the area of observed exposure is 100 for PCE

. Per the HRS, t he d egradation factor is assigned a value of one due to the documentation of an ob served exposure to PCE

. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 100 , which is the highest combined value of all eligible substances

. (a) 100

6. Hazardous Waste Quantity

The ar ea footprint s of the 116 multi

- subunit structures and two occupied structures (241 occupied units) in the area s of observed exposure and subsurface contamination are unknown. Therefore, a value of 1, 740 ft 2 per regularly occupied unit was used in calculating a hazardous waste quantity , which was used to select a hazardous waste quantity factor value using HRS Table s 2

- 5 and 2

- 6. (a) 10 ,0 00

7. Waste Characteristics (subject to a maximum of 100)

The to xicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 6 was used to select a waste characteristics factor category value of 32 from HRS Table 2

- 7. 100 32

Targets:
8. Exposed Individual As there is at least one individual in a regularly occupied structure that is exposed to Level I contaminant concentrations, a value of 50 is assigned. 50 50

9. Population:
9a. Level I Concentrations
The population living in the six regularly occupied structures containing (b) 130.2

### Page D -1 8 concentrations of PCE above the applicable health

- based benchmark of 9. 3 μg/m 3 (Cancer Risk Screening Concentration) is unknown; using an average of 2. 17 persons per household for the area in which the site is located results in 13.02 people exposed to Level I concentrations , which are then multiplied by a weighting factor of 10

. 9b. Level II Concentrations The population living in the 10 6 regularly occupied structures and multi

- subunit structures (i.e., 43 duplex structures
, 3 triplex structures , 6 units from duplex structures not scored as Level I , and 5 units from duplex structures where only one tenant space is located above an AOE ) located within the area of o bserved exposure with inferred Level II contamination is unknown; using a n average of 2.1 7 persons per household for the area in which the site is located results in a population of 23 0

. 02

. (b) 2 30

. 02

9c. Population within Area(s) of Subsurface Contamination
There are 125 regularly occupied structures and multi

- subunit structures ( 54 duplexes, 4 triplexes, 2 single family homes, and 3 units in duplex structures where only one tenant space is located above an ASC) within the ASC that are delineated with ground water samples

. In addition to these regularly occupied structures, there are two multi

- unit structures (4 units) that have documented levels of PCE meeting HRS observed release criteria in subslab samples within five feet of the structure.
Per draft HRS addition Table 5

- 20, samples delineated by ground water samples receive a weighting factor of 0.1 and samples with documented levels of PCE meeting HRS observed release criteria in subslab samples within five feet of the structure receive a w eighting factor of 0.4. The actual population living in these structures is unknown. Per the draft HRS addition, using the average of 2. 17 persons per household for the area in which the site is located results in a population estimate of 30.59. (b) 3 0.59

9 d

. Total Population (lines 9a + 9b + 9c) (b) 390.81
10. Resources

One church was 5 is assigned. identified within the ASC. Per the draft HRS addition, a value of 5 5

11. Targets (lines 8 + 9 d + 10) (b) 445.81 Subsurface Intrusion Component Score
12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 d (subject to a 100 95.10

Soil Exposure and Subsurface Intrusion Pathway Score
13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 95.10

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c No specific maximum value applies to factor.
d Do not round to nearest integer



## .

HRS Site Score

2 2 2 0 2 0 2 √[ ( S gw + S sw + S sessi + S a 2 )/4] = √ [( + + 95.10 2 +0 2 ) /4] 100 47.55

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# Subsurface Intrusion Test Site 00 4 ( January 2016 )

Site Description T est site 004 is located in central Maryland, within an area containing a mixture of residential, commercial and industrial land use types. Historical operations at a former precious metal recovery operation resulted in a release of chlorinated solvents to shallow ground water and soils immediately surrounding the facility. The site includes a residential area comprised of row houses located between two noncontiguous property parcels. The two noncontiguous property parcels were previously the location of a former precious metal recovery operation. In 1981, the State of Maryland reported the property parcels to the U.S. Environmental Protection Agency (EPA) and requested assistance after discovering deteriorating and damaged tanks, containers and drums that were leaking their contents to the environmen t. EPA assessed the site and commenced an emergency response action, which was completed in December 1981. In 2002 the Maryland Department of the Environment (MDE) collected air samples from locations on or adjacent to the two noncontiguous property parcel s. Results of these samplesindicated the presence of volatile organic compounds (VOCs) inside the building located at the stateowned parcel. Further air testing at the site in November 2003 confirmed this finding and indicated the presence of VOCs in the air inside a building adjacent to the vacant property parcel. In November and December 2005, MDE conducted a more detailed investigation of the ground water and soil vapor beneath the homes separating the two noncontiguous property parcels. Results of thi s investigation showed that ground water contamination from the parcels was migrating beneath many of the intervening homes. Soil gas and indoor air testing conducted for MDE between June 2007 and August 2008 in six of the twenty row houses indicated vapor intrusion has occurred in all six tested houses. As of 2010 installation of vapor intrusion mitigation systems in three homes had begun.

The s ite includes an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. The hazardous substances documented to be present in the AOE include tetrachloroethylene (PCE), trichloroethylene (TCE) and vinyl chloride

. The structures within the AOE include 17 occupied structures and 1 multi -subunit structure.

The site additionally includes an area of subsurface contamination (ASC) delineated by ground water and soil gas samples meeting observed release criteria. There are no additional structures within the ASC.

Scoring Limitations and Assumptions Besides the global li mitations and assumptions made for all test sites listed at the beginning of this appendix, the following site -specific limitations and assumptions were made in the scoring of this site:

• For sampling events where no appropriate background sample was available, it was assumed that the background level to compare against release contaminant concentrations was non

- detect for manufactured substances (i.e., PCE, TCE and vinyl chloride). Therefo re, per the draft HRS Subsurface Intrusion (SsI) Addition (draft HRS addition), an observed exposure or observed release was documented when a release contaminant concentration equaled or exceeded its appropriate reporting limit.

• It is assumed that all reg ularly occupied structures within the AOE have a non-zero structure containment value.

### Page D -2 0 

### • Indoor air samples meeting the observed exposure criteria are not due to the presence of potential indoor sources of vapor- forming chemicals, such as household cleaners, and the significant increase in hazardous substance levels are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full- time worker per workplace if more specific information is not available.

• Per the draft HRS addition an assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi -subunit structures)

• Based on the definitions provided for qualified data, it is assumed that the J-qualified data used to identify observed exposure samples were above their applicable reporting limit.

• Information used in the scoring of the test sites (inclu ding aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• It is assumed that all ground water sampling data used in this analysis, including samples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• Although some reports indicate the presence of vapor mitigation systems, it is assumed that cracks

a nd/or preferential pathways into a structure still exist and that all structures have a containment value greater than zero.

• It is assumed that any vapor intrusion mitigation systems present in an occupied structure do not represent a permanent remedial ac tion.

• Every regularly occupied residential structure within the AOE and ASC is occupied with the average number of persons per household (2.48) for the city in which the site is located ; with one exception, one residence is documented as having four occupants based on a 2009 In- home Sampling Home Survey Form. The city average number of persons per household is used as the city in which the site is located is classified as an independent city. This value is assumed to be sufficiently close to an appropriate county average to not significantly impact the HRS site score.

The figure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the Hazard Ranking System (HRS). The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List (NPL) and it is likely that additional evaluation and sampling would be necessary to determine if the site would qualify for listing.

As part of this li mited assessment, Test Site 004 is evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at the site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration p athway, air migration pathway or the soil exposure component of the draft soil exposure and subsurface intrusion pathway.

### Page D -2 1 

# Subsurface Intrusion Test Site 00 4 ( Figure 4 )

Site Diagram

### Page D -2 2 

## Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Likelihood of Exposure:
1. Observed Exposure An observed exposure by chemical analysis for mul tiple hazardous substances, including PCE, TCE and vinyl chloride , was documented in seven regularly occupied structures. 550 550

2. Potential for Exposure
Per the draft HRS, the p otential for exposure factor the documentation of an observed exposure. was not evaluated based on

2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15

- 2d. Vapor Migration Potential 25

- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics:

- 5. Toxicity/ D egradation The highest toxicity value for the substances documented in the ASC and the AOE is 1 0 ,000 for vi nyl c hloride

. Per the draft HRS, as vinyl chloride was found in a sample that met observed exposure criteria, a degradation factor value of
one is assigned

. The toxicity factor value is multiplied by the degradation factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10,000

6. Hazardous Waste Quantity
The actual basal area footprint s of the 17 regularly occupied structures in the AOE and ASC are unknown. Per the draft HRS addition, for Tier D, Area, a value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity. These values were used to select a hazardous waste quantity factor value using HRS Tables 5

- 18 (draft addition) and 2

- 6. (a) 100

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 6 was used to select a waste characteristics factor category value of 32 from the draft HRS Table 2

- 7. 100 32

Targets:
8. Exposed Individual

T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations . Per the draft HRS, value of 50 was assigned. a 50 50

9. Population:

9a. Level I Concentrations
The actual population living in the six regularly occupied structures and one multi

- (b) 1 51.8

### Page D -2 3 unit structure (with at least one full time worker) containing TCE and/or PCE 3 above their respective health

- based benchmarks of 0.4 3 μg/m 3 and 9. 3 μg/m (Cancer Risk Screening Concentration s ) is unknown

. Per the draft HRS addition, the total number of workers are divided by 3 (1/3 = 0.3) and summed with the population residing in the remaining structures. U sing the average of 2. 48 persons per household for the city in which the site is located results in a population estimate of 15.18 ( 1 4.88 +0.3 = 15.18) people exposed to Level I concentrations

. This value is then multiplied by a weighting factor of 10 per the draft HRS addition

.
9b. Level II Concentrations
The actual population living in nine of the 10 regularly occupied structures located within the AOE , and not subject to Level I concentration levels, is unknown. One of the regularly occupied structures was documented in a survey to contain 4 persons. Per the draft HRS, applying the c ity average of 2. 48 persons per household to each of the aforementioned nine structures and including the four residents documented in the final occupied structure results in a population estimate of 26.32 people being exposed to Level II concentrations

. (b) 26.32

9c. Population within Area(s) of Subsurface Contamination No populations within the ASC not already evaluated as subject to Level I or contaminant concentrations were identified

. II (b) 0

9d

. Total Population (lines 9a + 9b + 9c) (b) 17 8.12

10. Resources
No resources were identified a value of 0 is assigned

. within the AOE or ASC. Per the draft HRS addition
, 5 0

11. Targets (lines 8 + 9 d + 10) (b) 2 28.12 Subsurface Intrusion Component Score
12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 c (subject to a 100 48.66

Soil Exposure and Subsurface Intrusion Pathway Score
13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 48.66

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to the nearest integer.

HRS Site Score Maximum Value Value Assigned

2 √[ ( S gw + 2 S sw + 2 S s es si + S a 2 )/4] = √ [( 0 2 + 0 2 + 48.66 2 +0 2 )/4] 100 24.33

### Page D -2 4 

# Subsurface Intrusion Test Site 00 5 ( January 2016 )

Site Description Test Site 005 is located in southeastern Pennsylvania, within an area of mixed residential, commercial and industrial use. Historical operations at nearby facilities have resulted in a release of chlorinated solvents to shallow ground water and soils surrounding commercial and residential properties. The Envi ronmental Protection Agency ( EPA ) initiated a r emoval a ssessment at the Site in September 2003 and continued investigations at the site through January 2006 . The results of the r emoval a ssessment revealed the presence of trichloroethylene (TCE) in ground water, soil gas vapor and indoor air at both commercial and residential properties in the area of investigation. EPA Removal Program installed indoor air mitigation systems at three priva te residences which are impacted by the Site. The site was originally scored using only the ground water migration pathway, but would not score high enough to be considered National Priorities List ( NPL ) eligible based on this score alone.

The s ite includ es an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. The hazardous substances documented to be present in the AOE were tetrachloroethylene (PCE), TCE and cis-1,2-dichloroethylene (DCE). The structures w ithin the AOE include three regularly occupied structures

.

The site additionally includes an area of subsurface contamination (ASC) delineated by soil vapor and ground water samples meeting observed release criteria. The additional structures within the ASC include 45 regularly occupied structures.

Key Scoring Limitations/AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptions were mad e in the scoring of this site:

• For sampling events where appropriate background samples were not collected, it is assumed that the background level to compare release contaminant concentrations against is non

- detect for the manmade substances.

• Data obtained from multiple sampling events were used to delineate subsurface contaminant plumes. Therefore, a minimal approach was used when delineating areas of subsurface contamination based on the available information. However, it is likely that with additional data the areas of subsurface contamination could be larger than shown in this evaluation.

• Based on the information available, it was not possible to determine if occupied structures identified within the areas of observed exposure and subsurfac e contamination contained multiple tenant spaces.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site

.

• It is assumed that all regularly occupied structures within the AOE and ASC have a non

- zer o structure containment value.

• Indoor air samples meeting the observed exposure criteria are not due to the presence of potential indoor sources of vapor- forming chemicals, such as household cleaners, and the significant

### Page D -2 5 

### increase in hazardous substance lev els are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

time worker per workplace if more specific information is not available.

• Worker population at the commercial facility is determined to be 96 employees. Per the draft Hazard Ranking System (HRS) addition, workers are considered full time unless information is available identifying the number of full -time and part- time workers.

• An indoor air temperature of 25 °C and 1 standard atmosphere were assumed when converting indoor air sampling data provided in units of parts per billion by volume (ppbv) for comparison to health

- based benchmarks (i.e., from ppbv to micrograms per cubic meter [μg/m 3 

### ]).

• Per the draft Hazard Ranking System ( HRS ) addition, a n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi -subunit structu res).

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• It is assumed that all ground water sampling data used in this analysis, including samples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• In several instances, structures were classified as duplex units based on aerial imagery and this information has not been validated. It is also assumed that each structure and/or duplex unit identified is currently occupied.

• Although some reports indicate the presence of mitigation systems, it is assumed that these systems are not a permanent remedy and that preferential pathways into a structure still exist (i.e., all structures have a containment value greater than zero).

The figure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the NPL and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As p art of this limited assessment, t est site 003 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

.

### Page D -2 6 

# Subsurface Intrusion Test Site 00 5 ( Figure 5 )

Site Diagram

### Page D -2 7 

## Tab le 5 -11 Ground Water Migration Pathway Scoresheet

Factor Categories and Factors Maximum
Value Value Assi g ned
Ground Water Migration Pathway

Lik elihood of Release to an Aquifer:

1. Observed Release Observed release concentrations of cis

- 1,2

- DCE and TCE attributable to the source

were documented in the interconnected aquifers based on monitoring wells and one public supply well (TCE only). 550 550

2. Potential to Release: Potential to release was not evaluated based on observed exposure per the HRS. 500 -

2a. Containment 10 - 2b. Net Precipitation 10 - 2c. Depth to Aquifer 5 - 2d. Travel Time 35 - 2e. Potential to Release [ lines 2a * ( 2b + 2c + 2d ) ] 500 - 3. Likelihood of Release ( higher of lines 1 and 2e ) 550 550
Waste Characteristics: Concentrations of TCE, cis

- 1,2

- DCE, and vinyl chloride were documented in the unconfined contaminated soil

source.

4. Toxicity/Mobility The highest toxicity/mobility value for the hazardous substances documented in the ground water observed release documentation and the contaminated soil source documentation is 10,000 for vinyl chloride. (a) 10,000

5. Hazardous Waste Quantity The quantity of the contaminated soil source is unknown but greater than zero. Because there are no drinking water wells subject to actual contamination and the hazardous constituent quantity cannot be adequately determined, a default of 10 may be assigned. (a) 10

6. Waste Characteristics 100 18 Targets :

7. Nearest Well The closest drinking water well to the contaminated soil source is a p ublic s upply w ell, which is locate d between 0.5 and 1 mile from the source. 50 9

8. Population:

8a. Level I Concentrations No population subject to Level I concentrations was identified. (b) 0

8b. Level II Concentrations No population subject to Level II concentrations was identified. (b) 0

### Page D

- 28 8c. Potential Contamination One public supply well is located between 0.5 and 1 mile from the contaminated soil source and serves a population of 1,141. Two public supply wells are located between 1 and 2 miles of the contaminated soil source and serve a combined population of 2,282. Four public supply wells are also located between 1 and 2 miles of the contaminated soil source and serve a combined population of 11,000. Five publ ic supply wells are located between 2 and 3 miles from the source and serve a combined population of 7,000. One public supply well is located between 3 and 4 miles from the source and serve a population of 1,400 people. Using HRS Table 3

- 12 a distance

weig hted population value of 4,271 is calculated

. (b) 427.1

8d. Population ( lines 8a + 8b + 8c ) (b) 427.1

9. Resources Insufficient information exists to determine a score for resources. 5 0

10. Wellhead Protection Area Insufficient information exists to determine a score for a wellhead protection area. 20 0

11. Targets ( lines 7 + 8d + 9 + 10 ) (b) 436.1 Ground Water Migration Score For An Aquifer:

12. Aquifer Score [ ( lines 3 * 6 * 11 ) / 82,500 ] c 100 52.33 Ground Water Migration Pathway Score:

13. Pathway Score (S gw ), (highest value from line 12 for all aquifers evaluated) c 100 52.33

a 

### Maximum value applies to waste characteristics category. b 

### Maximum value not applicable.

c 

### No specific maximum value applies to factor. d 

### Do not round to nearest integer.

### Page D

- 29 

## Table 5

- 11 Subsurface Intrusion Component Scoresheet Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Likelihood of Exposure: 1. Observed Exposure An observed exposure by chemical analysis for TCE was documented in three regularly occupied structures. 550 550

2. Potential for Exposure Potential for exposure was not evaluated based on the documentation of an observed exposure per the HRS. 2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15

- 2d. Vapor Migration Potential 25

- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics:

- 5. Toxicity/ D egradation The highest toxicity value for the substances documented in the area of subsurface contamination and/or the area of observed exposure is 1 0 ,000 for vinyl chloride

. Per the draft HRS, a lthough vinyl chloride was not found in a sample that met observed exposure criteria, as the degradation half

- life of Vinyl Chloride is greater than100 days
, a degradation factor value of one is applied

. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10,000

6. Hazardous Waste Quantity The area footprint s of the approximately 48 regularly occupied structures in the areas of observed exposure and subsurface contamination are unknown. Therefore, a value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity, which was used to select a hazardous waste quantity factor value using HRS Tables 2

- 6 and 5

- 18

. (a) 100

7. Waste Characteristics (subject to a maximum of 100) The toxicity/biodegradation and hazardous waste quantity factor values were multiplied to calculate a value of 1x10 6 , which was used to select a waste characteristics factor category value of 32 from HRS Table 2

- 7. 100 32

Targets:
8. Exposed Individual As there is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations, a value of 50 is assigned. 50 50

9. Population:
9a. Level I Concentrations
The actual population living in the three regularly occupied structures containing TCE above the applicable health

- based benchmark of 0.43 μg/m 3 (Cancer Risk Screening Concentration) is unknown; using a county average of 2. 62 persons (b) 78.60

### Page D -3 0 per household results in 7. 86 people exposed to Level I then multiplied by a weighting factor of 10. concent rations, which are

9b. Level II Concentrations
No oc cupied structures subject to Level II this evaluation

. concentrations w as identified as part of (b) 0

9c. Population within Area(s) of Subsurface Contamination There is one regularly occupied structure within the ASC that is delineated with a subslab sample located within five feet of the structure. There are 29 regularly occupied structures within the ASC that are delineated with soil vapor samples approximately eight feet bgs ( one of these structures includes the commercial facility with 96 full

- time workers and another eight of these structures contain at least one full

- time worker) ; additionally, 15 regularly occupied residential structures within the ASC that are delineated with ground water samples approximately 10 feet bgs (three of these structures contain at least one full

- time worker). Per the draft HRS, where w orker population is unknown, it is assumed that at least 1 full

- time worker per facility is present. The actual population living in these structures is unknown. Per the draft HRS addition, using the borough average of 2.62 persons per household results in a population estimate of 1.048 people (based on a subslab sample located within 5 feet of the struct ure); 17.4 ( 10.48 +6.93 = 17.4) (based on soil gas samples); and 3.24 ( 3.14 +0.1 = 3.24) (based on ground water samples). These population estimates were multiplied by respective weighting factor s of 0.4 (subslab within 5 feet of an occupied structure), 0.2 (soil gas) and 0.1 (ground water) using the draft HRS . These three values were then summed to calculate the total population of 14.67 within an area of subsurface contamination (b) 21.68

9d

. Total Population (lines 9a + 9b + 9c) (b) 100.28

10. Resources No resources were identified within the established areas of observed exposure and subsurface contamination

. 5 0

11. Targets (lines 8 + 9 d + 10) (b) 150.28 Subsurface Intrusion Component Score
12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 c (subject to a 100 32

. 05

Soil Exposure and Subsurface Intrusion Pathway Score
13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 32.05

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer



## .

HRS Site Score √[ ( S gw 2 + S sw 2 + S s es si 2 + S a 2 )/4] = √ [( 52.33 2 + 0 2 + 32.05 2 +0 2 )/4] 100 30.68

### Page D -3 1 

# Subsurface Intrusion Test Site 00 6 ( January 2016 )

Site Description Test site 006 is located in north

- central Texas within an area of mixed residential, commercial and industrial use. Test Site 006 consists of a release of hazardous substances from a facility that historically conducted machining and metal forging operations and regularly occupied structures within documented

area s of observed exposure (AOE) and an area of subsurface contamination (ASC) surrounding the AOE. Trichloroethylene (TCE) contamination was first identified at the facility during an environmental property assessment in 2002 . A dditional investigat ions identified ground water contaminated predominantly with TCE underlying the facility and adjacent residential areas. In 2008, the U.S. Environmental Protection Agency ( EPA ) conducted a vapor intrusion sampling event at 18 structures overlying the groun d water plume , which documented indoor air samples containing levels of TCE and tetrachloroethylene ( PCE ) meeting observed exposure criteria

.
Addit ionally, b ased on the available information, sufficient data to evaluate the Hazard Ranking System ( HRS ) air and surface water migration pathways and the soil exposure pathway was not available. However, given the presence of contaminated soil and ground water documented at the facility and site during previous investigations, the site could be evaluated using the soil exposure and ground water migration pathways if additional information became available.

Scori ng Limitations/AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptions were identified for scoring this site:

• It is assumed that the different structure types present in the areas of observed exposure and subsurface contamination are sufficiently similar to each other for HRS scoring purposes.

• A single indoor air sample collected within an occupied structure outside the AOE and ASC can be used as a background level to compare against release samples.

• Data obtained from multiple sampling events were used to delineate subsurface contaminant plumes

. Therefore, a minimal approach was used when delineating areas of subsurface contamination based on the available informa tion. However, it is likely that with additional data the areas of subsurface contamination could be larger than shown in this evaluation.

• Based on the information available, it was not possible to determine if occupied structures identified within the areas of observed exposure and subsurface contamination contained multiple tenant spaces.

• All sample locations are approximate and esti mated based on figures identifying those sample locations in relation to streets and industrial facilities.

• It is assumed that all regularly occupied structures within the AOE and ASC have a non

- zero structure containment value.

• Indoor air samples meeting the observed exposure criteria are not due to the presence of potential indoor sources of vapor- forming chemicals, such as household cleaners, and the significant increase in hazardous substance levels are attributable at least i n part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC . Worker population data is assumed to be at least 1 full

- time worker per workplace if more specific information is not available.

### Page D -3 2 

### • An indoor air temperature of 25 °C and 1 standard atmosphere were assumed when converting indoorair sampling data provided in units of parts per billion by volume (ppbv) for comparison to healthbased benchmarks (i. e., from ppbv to micrograms per cubic meter [μg/m 3 

### ]).

• Per the dra ft HRS addition, an assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi -subunit structures).

• Information used in the scoring of the test sites (including aerial im agery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• The depths at which the ground water samples were collected is unknown; however, it is assumed that the wells were screened in the same relative portion of the surficial ground water and are sufficiently similar to not cause a significant difference in contaminant levels. It is also assumed that the samples were collected at a distance greater than five feet from a regularly occupied structure’s foundation when assigning target weight ings to ASC populations.

• As data for all identified wells in the site area were not available, with additional data, the area of subsurface contamination could be larger in size.

The figure and site score presented for this test site are for the purpose o f testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL), and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.
As p art of this limited assessment, the Test site 002 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

### Page D -3 3 

# Subsurface Intrusion Test Site 00 6 ( Figure 6 )

Site Diagram

### Page D -3 4 

## T able 5

- 11 Subsurface Intrusion Component Scoresheet Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Likelihood of Exposure:
1. Observed Exposure An observed exposure by chemical analysis for TCE was documented in seven regularly occupied structures and for PCE in two regularly occupied structures. 550 550

2. Potential for Exposure Potential for exposure was not evaluated based on the documentation of an observed exposure per the HRS. 2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15

- 2d. Vapor Migration Potential 25

- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics:

- 5. Toxicity/ D egradation The highest toxicity value for the substances documented in the ASC and/or the AOE is 1 0 ,000 for vinyl chloride

. Per the HRS, a lthough vinyl chloride was not found in a sample that met observed exposure criteria, as the degradation half

life of Vinyl Chloride is greater than100 days , a degradation factor value of one is applied

. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10,000

6. Hazardous Waste Quantity
The actual basal area footprint s of the 10 4 regularly occupied structures in the AOE and ASC are unknown. Therefore, as stated in the HRS, a minimum value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity, which was used to select a hazardous waste quantity factor value using HRS Tables 5

- 18 and 2

- 6. (a) 10,000

7. Waste Characteristics (subject to a maximum of 100) The toxicity/biodegradation and hazardous waste quantity factor values were multiplied to calculate a value of 1x10 8 , which was used to select a waste characteristics factor category value of 100 from HRS Table 2

- 7. 100 100

Targets:
8. Exposed Individual
T

here is at least one individual in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations

. Per the HRS, a value of 50 is assigned. 50 50

9. Population:
9a. Level I Concentrations The population living in the seven regularly occupied structures containing TCE above the applicable health

- based benchmark of 0.43 μg/m 3 (Cancer Risk Screening Concentration) is unknown . Per the HRS, using the c ounty average of 2. 7 7 persons per household results in a population estimate of 19

. 3 9 people (b) 193. 9

### Page D -3 5 exposed to Level I of 10. concentrations, which are then multiplied by a weighting factor

9b. Level II Concentrations The po pulation living in the two regularly occupied structures with documented exposure to Level II concentrations of PCE and the 1 4 regularly occupied structures inferred to be exposed to contamination is unknown . Per the HRS, using the c ounty average of 2. 77 persons per household results in a population estimate of 44.32 people exposed to Level II concentrations

. (b) 44.32

9c. Population within Area(s) of Subsurface Contamination The population living in the 81 regularly occupied residential structures within the ASC , is unknown (77 regularly occupied structures and 4 multi

- subunit structures with at least one full

- time worker)

. Per the draft HRS addition, the total number of full

- time workers are divided by 3 (4/3 = 1.3) and summed with the population residing in the remaining structures. U sing the c ounty average of 2.7 7 persons per household results in a population estimate of 214.5 ( 21 3.2 +1.3 = 214.5) people in the ASC. As the depth s of the ground water samples used to delineate the ASC are unknown and assumed to be greater than five feet from all structure foundations , this population estimate wa s multiplied by a weighting factor of 0.1 using HRS Table 5

- 20. This results in a population estimate of 21. 4. (b) 21. 4

9d

. Total Population (lines 9a + 9b + 9c) (b) 259. 62

10. Resources
One religious facility assigned. is located within the ASC. Per the HRS, a value of 5 is 5 5

11. Targets (lines 8 + 9 d + 10) (b) 314

. 62 Subsurface Intrusion Component Score
12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 c (subject to a 100 100

Soil Exposure and Subsurface Intrusion Pathway Score
13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 100

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer



## .

HRS Site Score Maximum Value Value Assigned √[ ( S gw 2 + S sw 2 + S sessi 2 + S a 2 )/4] = √ 0 2 + 0 2 + 100 2 +0 2 )/4] 100 50

### Page D

- 36 

# Subsurface Intrusion Test Site 00 7 ( January 2016 )

Sit e Description Test site 007 is located in the District of Columbia
, within an area of commercial and residential land use types and is immediately adjacent to the hospital complex . Dry cleaning operations have reportedly been ongoing for approximately 60 years at the facility. These historical operations have resulted in a release of chlorinated solvents to s hallow ground water and soils immediately surrounding the facility
, as has been documented in several environmental investigations conducted in 2013 and 2014.

The site includes an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure crite ria . The hazardous substances documented to be present in the AOE were tetrachloroethylene (PCE), trichloroethylene (TCE) and cis -1,2-dichloroethene among other volatile organic compounds (VOCs) . The structures within the AOE include one s ingle -tenant occupied struct u re , a daycare facility with an estimated 48 enrolled children and the dry cleaning facility. Although

s ubsurface samples meeting observed release criteria are present at the site , an area of subsurface contamination (ASC) is not delineated as no additional targets were identified, and its inclusion would not alter the subsurface intrusion (SsI) component score.

Scori ng Limitations and Assumptions Besides the assumptions made for all test sites listed at the beginning of this appendix, the following site

specific limitations and assumptions were identified for scoring this site:

• For sampling events where no appropriate background sample was available, it was assumed that the background level to compare against release contaminant concentrati ons was non
- detect for manufactured substances (e.g., PCE). Therefore, per the draft Hazard Ranking System ( HRS ) Subsurface Intrusion ( SsI ) Addition, an observed exposure or observed release was documented when a release contaminant concentration equaled or exceeded its appropriate reporting limit.

• I t is assumed that all regularly occupied structures within the AOE ha ve a non-zero structure containment value.

• Indoor air samples meeting the observed exposure criteria are not due to anthropogenic sources (e.g., potential indoor sources of vapor- forming chemicals, such as household cleaners ) and the significant increase in hazardous substance concentrations are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site.

• The regularly occupied residential structure within the AOE is occupied with the appl icable average number of persons per household for the District of Columbia (based on available U.S. Census data). At least one full

- time employee works at the dry cleaning and daycare facilit ies included in the evaluation

.

• For the purposes of population scored, the daycare is assumed to be at capacity.

### Page D

- 37 

### • An indoor air temperature of 25 ° C and 1 standard atmosphere were assumed when converting indoor air sampling data provided in units of parts per billion by volume (ppbv) for comparison to health

- based benc hmarks (i.e., from ppbv to micrograms per cubic meter [μg/m 3 

### ]).

• A n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structures)

.

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

The f igure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As p art of this limited assessment, test site 007 was evaluated using only the draft HR S subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

### Page D

- 38 

# Subsurface Intrusion Test Site 00 7 ( Figure 7 )

Site Diagram

### Page D

- 39 

### Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component
Likelihood of Exposure:

1. Observed Exposure An observed exposure by chemical analysis for PCE has been documented in 3 regularly occupied structures

. 550 550

2. Potential for Exposure
P er the draft HRS addition , the p otential for exposure factor was not evaluated based on the documentation of an observed exposure.

2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15
- 2d. Vapor Migration Potential 25
- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500
- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Toxicity/ D egradation The highest toxicity value for the substances documented in the AOE is 1
, 00 0 for TCE

. Per the draft HRS addition
, as TCE was found in a sample that met observed exposure criteria
, a degradation factor value of one is assigned

. The toxicity factor value is multiplied by the degradation factor value . T he toxicity/degradation factor value of 1 ,0 00, which is the highest combined value of all eligible substances, is assigned. (a) 1 ,0 00

6. Hazardous Waste Quantity The actual basal area footprints of the three regularly occupied structures in the AOE are unknown. Per the draft HRS addition , for Tier D, Area , a value of 1, 740 ft

2 per regularly occupied structure was used in calculating a hazardous waste quantity. These values were used to select a hazardous waste quantity factor value using HRS Tables 5- 18 (draft addition ) and 2

- 6. (a) 100

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 5 was used to select a waste characteristics factor category value of 18 using HRS Table 2

- 7. 100 18

### Page D -4 0 Factor Categories and Factors Maximum Value Value Assigned Targets:

8. Exposed Individual
T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations . Per the draft HRS addition
, a value of 50 was assigned. 50 50

9. Population:

9a. Level I Concentrations
Th e re are a reported total of 48 children attending the daycare facility, which contains concentrations above the applicable health

- based benchmark of 9.3 μg/m 3 (C ancer Risk Screening Concentration ) for PCE

. There are two workplaces located within the AOE . The actual number of employees associated with these workplaces is unknown. The refore, a minimum of one full

- time worker per workplace is assumed to be present for estimation purposes. Per the draft HRS addition the total number of full

- time workers are divided by 3 (2/3=0.6) and summed with the population estimate. Additionally, the actual population living in the one regularly occupied structure with documented exposure to Level I concentrations of PCE is unknown. Per the draft HRS addition, u sing the Washington, D.C. average of 2. 2 persons per household results in a total population estimate of 50.8 people exposed to Level I concentrations which was then multiplied by a weighting factor of 10

. (b) 508.0

9b. Level II Concentrations
No popu lation subject to Level II contaminant concentrations was identified as part of this evaluation. (b) 0

9c. Population within Area(s) of Subsurface Contamination No ASC was established as part of this evaluation. (b) 0

9d . Total Population (lines 9a + 9b + 9c) (b ) 508.0

10. Resources
No resources were identified within the AOE or ASC. Per the draft HRS addition
, a value of 0 is assigned. 5 0

11. Targets (lines 8 + 9 d + 10) (b) 558.0

Subsurface Intrusion Component Score

12. Subsurface Intrusion Component (lines 4 x 7 x 11 )/82,500 c (subject to a maximum of 100) 100 66.96

Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component + Subsurface Intrusion Component (subject to a maximum of 100) 100 66.96

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

### Page D -4 1 c Do not round to nearest integer



### .

HRS Site Score Maximum Value Value Assigned √[ ( S gw 2 + S sw 2 + S s es si 2 + S a 2 )/4] = √ [( 0 2 + 0 2 + 66.96 2 +0 2 )/4] 100 33.48

### Page D -4 2 

# Subsurface Intrusion Test Site 008 ( January 2016 )

Sit e Description Test site 008 is located in south- central Montana within an area of residential and commercial land use types. Historical releases possibly associated with two nearby dry cleaning operations have resulted in a release of chlorinated solvents to ground water in the area; the plume encompasses about 140 acres (1,000 ft wide by 8,000 ft long ). State -l ead preliminary assessments (PA), site inspections (SI) and expanded site inspections (ESI) were conducted at this site in Montana from 1993 to 2002 under the direction of the U.S. Environmental Protection Agency ( EPA ) Removal program since 2006.

The site includes an are a of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. T he hazardous substances documented to be present in the AOE were tetrachloroethylene ( PCE ) , trichloroethylene ( TCE ), 1,2 -dichloroethane (1,2- DCA ) and m ethyle ne

c hloride . The structures within the AOE include approximately 221 regularly occupied structures.

Alt hough, the site includes a large, well documented ground water plume that exceeds the boundaries of the established area of exposure, No area of subsurface contamination (ASC) was established as part of this evaluation and no population subject to potential contamination was identified as part of this evaluation.

Scori ng Limitations and Assumptions

• It is assumed that all regularly occupied structures within the AOE have a non-zero structure containment value.

• Indoor air samples meeting the observed exposure criteria are not due to anthropogenic sources (e.g., potential indoor sources of vapor- forming chemicals, such as household cleaners ) and the

s ignificant increase in hazardous substance concentrations are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE. Worker population data is assumed to be at least 1 full

- time worker per workplace if more specific information is not available.

• An indoor air temperature of 25 ° C and 1 standard atmosphere were assumed when converting indoor air sampling data provided in units of parts per billion by volume (ppbv) for comparison to health -based benchmarks (i.e., from ppbv to micrograms per cubic meter [μg/m 3 

### ]).

• A n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structu res)

.

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

• The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

### Page D -4 3 

### • It is assumed that all ground water sampling data used in this analysis, including samples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• Each structure identified was considered as a single occupied structure. Many of these structures might include apartments or duplex units , but for the purpose of th is evaluation each structure was only evaluated as one occupied structure

. (Garage structures were not counted as part of this evaluation even though some of them may contain apartments).

• Although some reports indicate the presence of vapor mitigation systems, it is assumed that cracks and/or preferential pathways into a structure still exist and that all structures have a containment value greater than zero.

• For indoor air samples, no unqualified background data were available. A qualified background sample result was used, and the EPA November 1996 Factsheet Using Qualified Data to Document an Observed Release and Observed Contamination ( EPA 540 -F-94-028 ) was employed; an adjustment factor of 10 was applied to the qualified background result prior to its

u se in setting observed exposure criteria.

The f igure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the Hazard Ranking System ( HRS ) . The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As pa rt of this limited assessment, t est site 008 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water mi gration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

### Page D -4 4 

# Subsurface Intrusion Test Site 00 8 ( Figure 8 )

Site Diagram

### Page D -4 5 

### Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component
Likelihood of Exposure:

1. Observed Exposure An observed exposure by chemical analysis for PCE, TCE, 1,2

- DCA and Methylene Chloride was documented in approximately 71 regularly occupied structures. 550 550

2. Potential for Exposure Potential for exposure was not evaluated based on the documentation of an observed exposure per the HRS.

2a. Structure Containment 10

- 2b. Depth to contamination 10
- 2c. Vertical Migration 15
- 2d. Vapor Migration Potential 25
- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500
- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Toxicity/ D egradation The highest toxicity value for the substances documented in the area of observed exposure is 1,000 for TCE

. Per the draft HRS addition, as TCE has been documented in an observed exposure, a degradation factor value of one is applied

. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 1,000, which is the highest combined value of all eli gible substances

. (a) 1,000

6. Hazardous Waste Quantity Approximately 2 28 Residential Structures and 7 businesses in the AOE have been identified based on a review of aerial im ages. Although several of the regularly occupied structures may include multi

- subunit structures (e.g., separate basement apartments), for the purpose of scoring this site using the proposed subsurface intrusion component, each unique structure has been counted only a single time in determining the hazardous waste quantity factor value. The actual basal footprint area of the 235 regularly occupied structures in the AOE is unknown. Per the draft HRS addition, for Tier D, Area, a value of 1,740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantit y. These values were used to select a hazardous waste quantity factor value using HRS Tables 5

- 18 (draft addition) and 2

- 6. (a) 10,000

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were 100 56

### Page D

- 46 multiplied to calculate a value of 1x10 6 , which was used to select a waste characteristics factor category value of 32 from HRS Table 2

- 7.

Targets:

8. Exposed Individual As there is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations for TCE. Per the draft HRS addition , a value of 50 is assigned. 50 50

9. Population:

9a. Level I Concentrations
The ac tual population living in the 26 regularly occupied structures containing concentrations above the applicable health

- based benchmark of 9.3 μg/m 3 (Cancer Risk Screening Concentration) for PCE is unknown

. There are approximately 7 apparent businesses located within the AOE . The actual number of employees associated with these workplaces is unknown. However, a minimum of one full

- time worker per workplace is assumed to be present. Per the draft HRS addition the total number of full

- time workers are divided by 7 (7/3=2.3) and summed with the population estimate. Per the draft HRS addition, using the county average of 2.40 persons per household results in a total population estimate of 62.40 people exposed to L evel I concentrations. This value is then multiplied by a weighting factor of 10, per the draft HRS addition

. (b) 647.0

9b. Level II Concentrations
The a ctual population living in the 195 (11 documented occupied structures and 184 inferred contamination) regularly occupied structures in the AOE containing concentrations below the applicable health

- based benchmark of 9.3 μg/m 3 (C

ancer Risk Screening Concentration) for PCE or with inferred Level II contamination is unknown. Per the draft HRS addition, u sing the county average of 2.40 persons per household results in a total population estimate of 484.8 people exposed to Level I I concentrations

. (b) 468.0

9c. Population within Area(s) of Subsurface Contamination Although, the site includes a large, well documented ground water plume that exceeds the boundaries of the established area of exposure, No ASC was established as part of this evaluation and no population subject to potential contamination was identified as part of this evaluation. (b) NS

9d . Total Population (lines 9a + 9b + 9c) (b ) 1115.0

10. Resources
No resources were identified within the AOE

. Per the draft HRS addition, a value of 0 is assigned. 5 0

11. Targets (lines 8 + 9 d + 10) (b) 1165.0
Subsurface Intrusion Component Score

12. Subsurface Intrusion Component (lines 4 x 7 x 11 )/82,500 d (subject to a maximum of 100) 100 100

### Page D

- 47 Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 100

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c No specific maximum value applies to factor.
d Do not round to nearest integer



### .

HRS Site Score √[ ( S gw 2 + S sw 2 + S s es si 2 + S a 2 )/4] = √ [( 0 2 + 0 2 + 100 2 +0 2 )/4] 100 50

### Page D

- 48 

# Subsurface Intrusion Test Site 00 9 ( January 2016 )

Sit e Description Test site 009 is located in south central Wisconsin within an area of commercial, industrial and residential land use types. It consists of an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria and an area of subsurface contamination (ASC) delineated by samples from multiple media meeting observed release criteria. Among the hazardous substances documented to be present in the AOE and A SC were tetrachloroethylene (PCE), trichloroethylene (TCE), vinyl chloride and cis -1,2-dichloroethe ne

.

The areas within the AOE and ASC include multiple regularly occupied structures and one industrial facility. Manufacturing- related activities have occurred on the industrial property since 1902 , which is currently operat ed as a metal die casting facility . Environmental investigations of the industrial facility and the surrounding area have identified PCE contamination in shallow ground water , potentially originating from a former aboveground storage tank and two historic vapor degreasers which used PCE as a solvent

. Reme diation efforts in the area have included soil remediation (e.g., a soil vapor extraction system)
, installation of an ozone sparge system to remediate ground water and the installation of multiple vapor mitigation systems in nearby occupied structures.

S coring L imitations and AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptions were identified for scoring this site:

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

time worker per workplace if more specific information is not available.

• The depths at which the subslab samples used in the evaluation were collected are unknown. It was assumed for evaluation purposes that they were located within a distance less than or equal to five feet from a structure’s foundation.

• For sampling events where no appropriate background sample was available, it was assumed that the background level to compare against release contaminant concentrations was non- detect for manufactured substances (e.g., PCE). Therefore, per the draft HRS ad dition , an observed exposure or observed release was documented when a release contaminant concentration equaled or exceeded its appropriate reporting limit.

• Although vapor mitigation systems are present in some occupied structures, it is assumed that these systems are not a permanent remedy and that all regularly occupied structures within the AOE and ASC ha ve a non-zero structure containment value.

• It is assumed that area remediation projects have not completely removed or remediated the subsurface contamination.

• A n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structures)

.

• Per the draft Hazard Ranking System ( HRS ) addition, a ceiling height of 8 feet was assumed in determining a waste quantity estimate for the industrial facility.

### Page D

- 49 

### The f igure and site score presented for this test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS. The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.

As p art of this limited assessment, T est s ite 009 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS. For example, although multiple municipal wells are present in the vicinity, such information as the numbers of people served by these wells or sampling data describing their condition were not available. Additionally, no sensitive species or habitat system s, including wetlands, were identified in the site’s vicinity

.

### Page D -5 0 

# Subsurface Intrusion Test Site 00 9 ( Figure 9 )

Site Diagram

### Page D -5 1 

### Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component
Likelihood of Exposure:

1. Observed Exposure An observed exposure by chemical analysis for PCE has been documented in 18 regularly occupied structures. 550 550

2. Potential for Exposure
P er the draft HRS addition , the p otential for exposure factor was not evaluated based on the documentation of an observed exposure.

2a. Structure Containment 10

- 2b. Depth to contamination 10

- 2c. Vertical Migration 15
- 2d. Vapor Migration Potential 25
- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500
- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Toxicity/ D egradation The highest toxicity value for the substances documented in the AOE and/or ASC is 1 0 ,000 for vinyl chloride. Per the draft HRS addition, as vinyl chloride was not found in a sample that met observed exposure criteria, as the depth to contamination below an area of subsurface contamination is less than 10 feet, a degradation factor value of one is assigned

. The toxicity factor value is multiplied by the degradation factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10,000

6. Hazardous Waste Quantity The actual basal area footprints of the 74 regularly occupied structures in the AOE and ASC are unknown. Per the draft HRS addition, a value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity. The one industrial facility identified in the AOE and ASC has been identified as being 130,000 ft 2 in size. Per the draft HRS addition, an assumed ceiling height of 8 fe et and the known size of 130,000 ft 2 , was used to calculate a volume for the industrial building. These values were used to select a hazardous waste quantity factor value using HRS Tables 5

- 18 (draft addition) and 2

- 6. (a) 10,000

### Page D -5 2 Factor Categories and Factors Maximum Value Value Assigned

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 8 was used to select a waste characteristics factor category value of 100 from the draft HRS addition Table 2

- 7. 100 100

Targets:

8. Exposed Individual
T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level II contaminant concentrations . Per the draft HRS addition, a value of 45 was assigned. 50 45

9. Population:

9a. Level I Concentrations
No popu lation subject to Level I contaminant concentrations was identified as part of this evaluation. (b) 0

9b. Level II Concentrations
The a ctual population living in the 42 ( 19 with documented exposure to Level II concentrations of PCE and the 23 with inferred contamination) regularly occupied structures in the AOE containing concentrations below the applicable health

- based benchmark of 9.3 μg/m 3 (C ancer Risk Screening Concentration ) for PCE or with inferred Level II contamination is unknown. There is one workplace located within the AOE . The nature and number of employees associated with this workplace is unknown. Therefore, a minimum of one full

- time worker is assumed to be present

. Per the draft HRS addition the total number of full

- time workers are divided by 3 (1/3=0.3) and summed with the population estimate. Per the draft HRS addition, u sing the county average of 2. 33 persons per household results in a population e stimate of 98.19 (97.86+0.3=98.19) people exposed to Level I I concentrations. (b) 98.19

9c. Population within Area(s) of Subsurface Contamination The actual population living in the 32 regularly occupied structures within the ASC is unknown. Per the draft HRS addition, for the 13 regularly occupied structures with subslab samples meeting HRS observed release criteria, u sing the county average of 2. 33 persons per household results in a population estimate of 30.29 people . This population estimate was t hen multiplied by a weighting factor of 0.4 using the draft HRS addition Table 5

- 20. For the 19 regularly occupied structures where contamination is inferred to be present based on surrounding samples meeting HRS observed criteria, using the county average of 2.33 persons per household results in a population estimate of 44.27. This population estimate was then multiplied by a weighting factor of 0.2 using the draft HRS addition Table 5

- 20. Per the draft HRS addition, the weighted population values are summ ed, resulting in a factor value of 20.97. (b) 20.97

9d . Total Population (lines 9a + 9b + 9c) (b ) 119.16

### Page D -5 3 Factor Categories and Factors Maximum Value Value Assigned

10. Resources
No resources were identified a value of 0 is assigned. within the AOE or ASC. Per the draft HRS addition, 5 0

11. Targets (lines 8 + 9 d + 10) (b) 164.16

Subsurface Intrusion Component Score

12. Subsurface Intrusion Component maximum of 100) (lines 4 x 7 x 11 )/82,500 c (subject to a 100 100

Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component maximum of 100) + Subsurface Intrusion Component (subject to a 100 100

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer



### .

HRS Site Score Maximum Value Value Assigned

2 √[ ( S gw + 2 S sw + 2 S s es si + S a 2 )/4] = √ [( 0 2 + 0 2 + 100 2 +0 2 )/4] 100 50 .00

# Subsurface Intrusion Test Site 0 10 ( January 2016 )

Site Description Test site 010 is located in eastern Missouri within an area of occupied structures. The U.S. Environmental Protection Agency discovered a ground water plume in a neighborhood and delineated the extent over multiple sampling events beginning in the summer of 1998. Two hazardous waste facilities are known to exist in the immediate vicinity of the ground water plume, including a former metal shaping facility and a life insurance facility where small scale dumping historically occurred in the mid 1960’s. The ground water plume consists of chlorinated solvents (TCE, PCE, CIS -1,2-DCE, Vinyl Chlo ride) and underlies a neighborhood consisting of a mix of regularly occupied structures and several single -story, multi-subunit
structures . Indoor air sampling has identified volatile organic compounds (VOCs) within the living space of numerous structures, including several contaminant concentrations exceeding cancer/non

- cancer benchmarks. In addition, subslab sampling has been conducted and elevated concentrations have been documented to be underlying several of structures.

The site includes an area of ob served exposure (AOE) delineated by indoor air samples meeting observed exposure criteria. T he hazardous substances documented to be present in the AOE were TCE, PCE and CIS -1,2- DCE . The structures within the AOE include 29 occupied structures . The site ad ditionally includes an area of subsurface contamination (ASC) delineated by subslab samples meeting observed release criteria. The structures within the ASC include 9 occupied structures

.
Scori ng Limitations and Assumptions Besides the assumptions made for all test sites listed at the beginning of this appendix, the following site

specific limitations and assumptions were made in the scoring of this site:

• It is assumed that all regularly occupied structures within the AOE and ASC have a non

- zero structur e containment value.

• Indoor air samples meeting the observed exposure criteria are not due to anthropogenic sources (e.g., potential indoor sources of vapor- forming chemicals, such as household cleaners ) and the significant increase in hazardous substance concentrations are attributable at least in part to the release(s) being evaluated.

• Data quality is sufficient for use in testing the draft subsurface intrusion component.

• Sampling locations presented are approximate and may not represent the actual extent of contamination at the site.

• Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

time worker per workplace if more specific information is not available.

• A n assigned area value of 1,740 square feet is used in determining a waste quantity estimate for all regularly occupied structures (including multi

- subunit structures)

.

• Information used in the scoring of the test sit es (including aerial imagery) is representative of current conditions.

Page D -5 4

### • The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• It is assumed that all ground water sampling data used in this analysis, including samples collected at the water table and from ten feet below the water table, represent a single surficial ground water layer.

• Aerial imagery, obtained through the maps.google.com online database was used to identify occupied structures for the purposes of this analysis. These images are assumed to represent current conditions and that all residences are occupied. In several instances, structures were classified as duplex units based on these images and this informatio n has not been validated. It is also assumed that each structure and/or duplex unit identified is currently occupied.

• Although some reports indicate the presence of vapor mitigation systems, it is assumed that cracks and/or preferential pathways into a structure still exist and that all structures have a containment value greater than zero.

The figure and site score presented for th is test site are for the purpose of testing the draft subsurface intrusion component addition to the Hazard Ranking System ( HR S) . The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would
q ualify for listing.
As part of this limited assessment, test site 010 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

Page D -5 5

# Subsurface Intrusion Test Site 0 10 ( Figure 10 )

Site Diagram

Page D

- 56

### Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component

Likelihood of Exposure:

1. Observed Exposure An observed exposure by structures. chemical analy sis was documented in 24 regularly occupied 550 550

2. Potential for Exposure Potential for exposure was exposure per the HRS. not evaluated based on the documentation of an observed

2a. S tructure Containment 10
- 2b. Depth to contamination 10
- 2c. Vertical Migration 15
- 2d. Vapor Migration Potential 25
- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Tox icity/ D egradation The highest toxicity value for the substances documented in the area of subsurface contamination and/or the area of observed exposure is 1 0 ,000 for vi nyl c hloride

. Per the HRS, as the degradation half

- life of vinyl chloride is greater than 100 days
, a degradation factor value of one is applied

. The degradation factor value is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 10,000, which is the highest combined value of all eligible substances

. (a) 10,000

6. Hazardous Waste Quantity The area footprint s of the 38 regularly occupied structures in the area s of observed exposure and subsurface contamination are unknown. Therefore, a value of 1, 740 ft 2 per regularly occupied structure was used in calculating a hazardous waste quantity, which was used to select a hazardous waste quantity factor value using HRS Tables 6 and 5

- 18

. 2- (a) 1 00

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied to calculate a value of 1x10 6 , which was used to select a waste characteristics factor category value of 100 from HRS Table 2

- 7. 100 32

Targets:

8. Exposed Individual As there is at least one individual in the area of observed exposure Level I contaminant concentrations, a value of 50 is assigned. that is exposed to 50 50



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- 579. Population:

9a. Level I Concentrations The po pulation living in the 19 regularly occupied structures containing TCE and/or PCE above the applicable health

- based benchmark of 0.43 and/or 9.3 μg/m 3 respectiv ely is unknown; using a county average of 2. 43 persons per household results in 46.17 people exposed to Level I concentrations, which are then multiplied by a weighting factor of 10. (b) 461.7

9b. Level II Concentrations The po pulation living in the 5 regularly occupied structures with documented expo sure to Level II concentrations of PCE and/or TCE and the 5 regularly occupied structures inferred to be exposed to contamination is unknown; using a county average of 2.4 3 persons per household results in 24. 3 people exposed to Level II concentrations

. (b) 24. 3

9c. Population within Area(s) of Subsurface Contamination

The 6 regularly occupied structures with documented subslab contamination meeti ng observed release criteria for PCE, TCE and/or Vinyl Chloride are assigned a weighting factor of 0.4 using HRS Table 5

- 20. The 3 regularly occupied structures inferred to be overlying a subsurface soil gas plume based on their location within the a rea of subsurface contamination are assigned a weighting factor of 0.2 using HRS Table 5

- 20. The 9 structures with in the area of subsurface contamination were multiplied by a county average of 2. 43 persons per household and their appropriate weighting factor to calculate a value of 7.26

. (b) 7.2 9

9d . Total Population (lines 9a + 9b + 9c) (b ) 49 3.29

10. Resources No resources were identified within the established areas of observed exposure and subsurface contamination

. 5 0

11. Targets (lines 8 + 9 d + 10) (b) 54 3. 29

Subsurface Intrusion Component Score

12. Subsurface Intrusion Component (lines 4 x 7 x 11 )/82,500 d (subject to a maximum of 100) 100 100

Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component + Subsurface Intrusion Component (subject to a maximum of 100) 100 100

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c No specific maximum value applies to factor.
d Do not round to nearest integer



### .

HRS Site Score

2 2 2 0 2 √[ ( S gw + S sw + S s es si + S a 2 )/4] = √ + 0 2 + 100 2 +0 2 )/4] 100 50



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# Subsurface Intrusion Test Site 0 11 ( January 2016 )

Sit e Description Test site 011 is located southwest of Minneapolis, Minnesota within a primarily residential neighborhood. It consists of an area of observed exposure (AOE) delineated by indoor air samples meeting observed exposure criteria and an area of subsurface contamination (ASC) delineated by sub- slab samples meeting observed release criteria. The hazardous substance tr ichloroethylene (TCE) was documented to be present in the ASC.

In 2009, the Minnesota Pollution Control Agency (MPCA) conducted an investigation to identify potential sources for a large contaminant ground water plume. Part of one study area, Area A
, was documented to have elevated concentrations of chlorinated solvents in ground water surrounding an occupied structure. Although this residential area with elevated contaminant ground water concentrations was determined not to be a likely source of the cont amination, subsequent soil gas and indoor air sampling events detected contaminants within 11 of the surrounding structures that were sampled. Sufficient information to identify the originating source of contamination for this area is not available.

Extensive sampling within the region has identified a larger subsurface contaminant plume; however, for purposes of this analysis, the AOE and ASC were limited to the areas surrounding the property since it is not apparent that the larger subsurface contam inant plume is continuous and associated with the release(s) being scored.

Scoring Limitations and AssumptionsBesides the assumptions made for all test sites listed at the beginning of this appendix, the following sitespecific limitations and assumptio ns were identified for scoring this site:

• Indoor air samples meeting the observed exposure criteria are not due to anthropogenic sources (e.g., potential indoor sources of vapor

- forming chemicals, such as household cleaners ) and the significant increase in hazardous substance concentrations are attributable at least in part to the release(s) being evaluated.

• Indoor air samples with concentrations exceeding residential indoor air screening levels are assumed to meet Hazard Ran king System ( HRS ) observed exposure criteria and are sufficient to identify Level I contamination.

• Data quality is sufficient for use in testing the draft subsurface intrusion component

.

• O bserved release/exposure samples and background samples are of sufficient similarity as to not cause the significant difference in contaminant levels observed

.

• Selected background sample locations and sample concentrations accurately represent background levels of the released substances

.

• Sampl e locations presented ar e approximate and may not represent the actual extent of contamination at the site.

• Information used in the scoring of the test sites (including aerial imagery) is representative of current conditions.

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### • 

## Available U.S. Census data is used to determine average number of persons per household residential targets in the AOE and ASC. Worker population data is assumed to be at least 1 full

- time worker per workplace if more specific information is not available. The contamination evaluated in the site scoring is either from a single release or from commingled plumes resulting from multiple releases.

• It is assumed that all regularly occupied structures within the AOE and the ASC have a non

- zero structure containment value. The figure and site score presented for t h is test site are for the purpose of testing the draft subsurface intrusion component addition to the HRS . The presented HRS site score and associated figure are not intended to justify placement on the National Priorities List ( NPL ) and it is likely that additional data collection, evaluation and sampling would be necessary to determine if the site would qualify for listing.
As part of this limited assessment, t est site 011 was evaluated using only the draft HRS subsurface intrusion component. While additional threats may exist at this site, sufficient data was not provided to evaluate the ground water migration pathway, surface water migration pathway, air migration pathway or the soil exposure pathway of the 1990 HRS.

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# Subsurface Intrusion Test Site 0 11 ( Figure 11 )

Site Diagram

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### Table 5

- 11 Subsurface Intrusion Component Scoresheet
Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component

Likelihood of Exposure:

1. Observed Exposure An observed expo sure by chemical analysis regularly occupied structures. has been documented in 11 550 550

2. Potential for Exposure Per the draft HRS addition, the p otential for exposure factor based on the documentation of an observed exposure. was not evaluated

2a. St ructure Containment 10

- 2b. Depth to contamination 10
- 2c. Vertical Migration 15
- 2d. Vapor Migration Potential 25
- 3. Potential for Exposure (lines 2a * (2b+2c+2d), subject to a maximum of 500) 500

- 4. Likelihood of Exposure (higher of lines 1 or 3) 550 550

Waste Characteristics: -

5. Tox icity/ D egradation The highest toxicity value for the substances documented in an ASC o r the area of observed exposure (AOE) is 1,000 for TCE . Per the draft HRS, although TCE was not found in a sample that met observed exposure criteria, as the depth to contamination below an area of subsurface contamination is less than 10 feet , a degradation factor of one is applied. The degradation factor is multiplied by the toxicity factor value to calculate the toxicity/degradation factor value of 1,000, which is the highest combined value of all eligible substances. (a) 1 ,0 00

6. Hazardous Waste Quantity Seventy

- two regularly occupied structures have been identified in the AOE and ASC, including one church with a minimum area of 11,700 ft 2

. The actual basal footprint area of each regularly occupied structure is unknown. Per the draft HRS addition
, a value of 1, 740 ft 2 per regularly occupied regularly occupied structure and a conservative value of 11,700 ft 2 was applied to the church to calculat e a hazardous waste quantity, which was used to select a hazardous waste quantity factor value using HRS Tables 5- 18 (draft addition) and 2

- 6. (a) 1 0,0 00

7. Waste Characteristics (subject to a maximum of 100) The toxicity/degradation and hazardous waste quantity factor values were multiplied and the resulting value of 1x10 7 was used to select a waste characteristics factor category value of 56 from draft HRS addition Table 2

- 7. 100 56

Targets:

### Page D -6 3 Factor Categories and Factors Maximum Value Value Assigned

8. Exposed Individual
T

here is at least one individual present in a regularly occupied structure in the AOE that is exposed to Level I contaminant concentrations . Per the draft HRS addition, a value of 50 was assigned. 50 50

9. Population:

9a. Level I Concentrations The actual population living in the 11 regularly occupied structures with documented exposure to Level I concentrations is unknown. Per the draft HRS addition, u sing the county average of 2. 38 persons per household results in a population estimate of 26. 18 people exposed to Level I concentrations . This value is then multiplied by a weighting factor of 10 per the draft HRS addition

. (b) 261 .8

9b. Level II Concentrations The actual population living in the 11 regularly occupied structures inferred to be exposed to Level II contamination is unknown. Per the draft HRS addition, u sing the county average of 2. 38 persons per household results in a population estimate of 26.18 people exposed to Level I I concentrations. (b) 26.18

9c. Population within Area(s) of Subsurface Contamination The actual population living in the 49 regularly occupied structures within the ASC is unknown. Per the draft HRS addition, for the 20 regularly occupied structures with subslab samples meeting HRS observed release criteria, u sing the county average of 2. 38 persons per household results in a po pulation estimate of 47.6 people . This population estimate was then multiplied by a weighting factor of 0.4 using the draft HRS addition Table 5

- 20 to get a value of 19.04

. For the 29 regularly occupied structures where contamination is inferred to be present based on surrounding samples meeting HRS observed criteria, using the county average of 2.3 8 persons per household results in a population estimate of 69.02

. There is one workplace located within the ASC . The nature and number of employees associated with this workplace is unknown. Therefore, a minimum of one full

- time worker is assumed to be present

. Per the draft HRS addition the total number of full

- time workers are divided by 3 (1/3=0.3) and summed with the population estimate (69.02+0.3=69.32). This population estimate was then multiplied by a weighting factor of 0.2 using the draft HRS addition Table 5

- 20 to get a value of 13.86. (b) 32.90

T

he weighted population values are summed, resulting in a factor value of 32.90

.

9d . Total Population (lines 9a + 9b + 9c) (b) 321. 5

10. Resources
A church was identified within the ASC. is assigned

. Per the draft HRS addition, a value of 5 5 5

11. Targets (lines 8 + 9 d + 10) (b) 376.5

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- 64 Factor Categories and Factors Maximum Value Value Assigned Subsurface Intrusion Component Score

12. Subsurface Intrusion Component (lines 4 x 7 x maximum of 100) 11 )/82,500 c (subject to a 100 100

Soil Exposure and Subsurface Intrusion Pathway Score

13. Soil Exposure Component + Subsurface Intrusion Component (subject to a maximum of 100) 100 100

a Maximum value applies to waste characteristics category. b Maximum value not applicable.

c Do not round to nearest integer.

HRS Site Score Maximum Value Value Assigned

2 √[ ( S gw 2 + S sw 2 + S s es si + S a 2 )/4] = √ [( 0 2 + 0 2 + 100 2 +0 2 )/4] 100 50.00